Boussinesq modeling of a rip current system

In this study, we use a time domain numerical model based on the fully nonl inear extended Boussinesq equations [Wei et al., 1995] to investigate surfa ce wave transformation and breaking-induced nearshore circulation. The ener gy dissipation due to wave breaking is modeled by introducing an eddy visco sity term into the momentum equations, with the viscosity strongly localize d on the front face of the breaking waves. Wave run-up on the beach is simu lated using a moving shoreline technique. We employ quasi fourth-order fini te difference schemes to solve the governing equations. Satisfactory agreem ent is found between the numerical results and the laboratory measurements of Haller et al. [1997], including wave height, mean water level, and longs hore and cross-shore velocity components. The model results reveal the temp oral and spatial variability of the wave-induced nearshore circulation, and the instability of the rip current in agreement with the physical experime nt. Insights into the vorticity associated with the rip current and wave di ffraction by underlying vortices are obtained.